The present invention relates to novel prostaglandins of the F series and vasopressors containing the same.
Prostaglandins of the F series (hereinafter referred to as PGFs) which contain a partial structure as a five-membered ring shown in the following formula: ##STR1## may be roughly divided into PGF.sub.1 .alpha.: ##STR2## in which the carbon atom at 5-position (referred to as C-5 hereinafter, such nominating is applied to other carbon) and C-6 are singly bonded, and PGF.sub.2 .alpha.: ##STR3## in which C-5 and C-6 are doubly bounded, and PGF.sub.3 .alpha.: ##STR4## in which C-5 and C-6 are, and C-17 and C-18 are are doubly bonded. For example, PGF.sub.2 .alpha. which exhibits marked oxytocic effect is clinically used to induce or promote pain at the last stage of pregnancy. Moreover, it is known to have vasopressor effect, however, the effect of PGF.sub.2 .alpha. is accompanied with preceding ephemeral vasorelaxation. Further, the typical PG effects on trachea, bronchus and intestine such as increase of airway resistance due to tracheal contraction and abdominal pain due to intestineal contraction, are simultaneously accompanied with vasopressor effect, therefore, there are problems to use the PGFs as vasopressors.
On the other hand, prostaglandin F metaboletes in which the bond between C-13 and C-14 is saturated, and C-15 is a carbonyl group, are found to exist in human and animal metabolites. These 13,14-dihydro-15-keto-prostaglandin Fs are shown in the formulae following: ##STR5## and are known as the metabolites of the corresponding PGF.sub.1 .alpha., PGF.sub.2 .alpha., and PGF.sub.3 .alpha. in vivo. These 13,14-dihydro-15-keto-PGFs scarcely exhibit any physiological activities that PGFs inherently possess, and have been reported as the physiologically-, and the pharmacologically- inactive metabolites (see, Acta Physiologica Scandinabia, 66, P 506(1988)).